Designing For Customer Displays

One of the common tasks an Application Developer faces is how to set up an application to work with customer displays.  Although different brands of displays may cause an ASCII code to vary a bit, the steps for implementing a customer display are pretty much the same for all of them.  The key is to realize that Touchnet does not recognize a customer display as such.  It thinks it’s sending output to a printer and, as far as we are concerned, that’s just fine.  We simply style for a display using the same steps we do for a printer; creating some print templates containing the images we want, defining the display as a printer, and programming the appropriate buttons and instruction chains with the appropriate commands to send the right template at the right time.
Creating the “Print” Templates

How many templates you need depends on how many different looks you want to send to the display.  However, here are a standard set of five that will work for most applications.

[img:1gp7jm95]http://www.possupport.net/dealer/kbase/images/display1.gif[/img:1gp7jm95]
CusPromo – This template clears and initializes the display.  It contains a promo message that displays on the screen in between orders.  CusPromo is normally sent from the Startup chain so that it will display when Touchnet is first run and at the beginning of each new order.  Use the I:Constant variable with two different values of Index.  This makes the promo message user changeable through the Constants section of Manager.

[img:1gp7jm95]http://www.possupport.net/dealer/kbase/images/display2.gif[/img:1gp7jm95]
CusItem – This template is used whenever a new item is ordered and contains the name and price of the item.  Send it from the OrderItm chain.  Use the Highlight Description and Highlight Price variables.

[img:1gp7jm95]http://www.possupport.net/dealer/kbase/images/display3.gif[/img:1gp7jm95]
CusTotal – Use this template when going to a tender screen.  It displays the total with tax using the Check Amount variable, mixed with text.

[img:1gp7jm95]http://www.possupport.net/dealer/kbase/images/display4.gif[/img:1gp7jm95]
CusChang – This template displays the amount tendered and the change due.  Send it from the Tender chain to coincide with display of the change on the screen.    Appropriately, it displays the Amount and Change Due variables, mixed with some text.

[img:1gp7jm95]http://www.possupport.net/dealer/kbase/images/display5.gif[/img:1gp7jm95]
CusCancl – Use this template when you cancel an item.  It displays the Highlight Description with some text.  Send it immediately prior to issuing the Cancel Item command.

There are a few other considerations when setting up templates for a display.

  1. Most of the displays will need some ASCII codes sent prior to the actual display.  These codes generally have the affect of clearing the display and telling it which mode to run in.  Consult the appropriate KBase document for the correct ASCII codes for the model you are using.
  2. 2×20 displays are the standard and all instructions in this tech tip are for 2×20 displays.
  3. Don’t forget!  You must remember to uncheck the Require PLU checkbox, or these templates will never get sent to the display.
  4. Be careful when you put a character in the 20th column.  On some displays, this may generate an undesired carriage return and cause your first line to scroll off the display. 

Defining the “Printer”

This is the easiest step.  Simply go into Printer Definitions, press Insert to Add a New Printer, give it a unique name, select the node and port that it is plugged in to, and define it as a Local printer.
Programming It To “Print”

To output to the display, you simply put a Do Template command to select the image you want to send to display, then issue a Print To command to tell Touchnet where to send it.

Now here’s where it gets a little tricky.  There just aren’t any simple rules I can give you as to where in your program you need to put these commands.  In Creating the Print Templates, I gave you some suggestions, but these assume that you have made a standard application with standard order flow and standard naming conventions, in which case why don’t you just use an existing application?  You need to examine each button and say do I need something to display here and, if so, what?

Don’t go crazy here.  Making every button display something is overkill and the customer will never be able to read the display as it continually flashes new messages.  However, by carefully fitting the above templates into the correct places as defined by the order flow of the application, you should wind up with a properly operating and professional looking customer display.